7th Grade Science: States of Matter (7.PS1.6)

A student designs an animation to visualize how the particles in a substance change when heat is added. How can the teacher verify that the animation is accurate?

• Adding heat creates the effect of increased spacing between particles.

• Adding heat creates the effect of increased particle size.

• Adding heat creates the effect of decreased spacing between particles.

• Adding heat creates the effect of decreased particle size.

Answer explanation

Adding heat increases the energy of particles, causing them to move faster and spread apart, which results in increased spacing between particles. This aligns with the correct choice.

Tags

NGSS.MS-PS1-4

A student is given a liquid compound in a beaker. Which of the following is the best way to describe this liquid compound?

• Definite shape, indefinite volume

• Indefinite shape, indefinite volume

• Definite shape, definite volume

• Indefinite shape, definite volume

Answer explanation

The correct choice is 'Indefinite shape, definite volume' because liquids take the shape of their container (indefinite shape) but have a fixed volume that does not change regardless of the container.

Tags

NGSS.MS-PS1-4

A waiter poured a glass of ice water. He noticed that the ice was still floating on top of the water in the glass fifteen minutes later. Why did the waiter find this phenomenon unusual?

• As ice cubes cool the water, the water becomes less dense than the ice; so after fifteen minutes, the ice should have begun to sink.

• Since the components of compounds cannot be physically separated, the ice and water should have been evenly distributed.

• The components of ice water have the same chemical formula (H₂O), making it a homogeneous mixture; so it should not separate.

• Most solid substances are more dense as compared to their liquid state, causing the solid to sink in the liquid; so he expected the ice to sink.

Answer explanation

Most solids are denser than their liquid forms, which is why they sink. The waiter expected the ice to sink in the water, making its floating state after fifteen minutes unusual.

How does the particle arrangement of water change when heated from 46°C to 102°C?

• Solid to liquid

• Liquid to gas

• Gas to liquid

• Solid to gas

Answer explanation

When water is heated from 46°C to 102°C, it transitions from a liquid state to a gas state (steam) as it reaches its boiling point. This change in particle arrangement signifies the conversion of liquid water to water vapor.

Tags

NGSS.MS-PS1-4

A student observes zinc turning from a solid to a liquid in a laboratory investigation. Which statement describes the change in zinc atoms while melting?

• The size of the zinc atoms decreased.

• The mass of the zinc atoms decreased.

• The zinc atoms lost their relative fixed positions.

• The zinc atoms were changed into atoms of another element.

Answer explanation

During melting, zinc atoms transition from a solid structure to a liquid state, losing their fixed positions. This allows them to move freely, which is characteristic of liquids, making 'lost their relative fixed positions' the correct choice.

Tags

NGSS.MS-PS1-4

The model shows water vapor in a cylinder topped with a piston. A student applies pressure to the water vapor by slowly pressing the piston. The temperature inside the cylinder remains the same. Which change will occur to the water molecules, and how will it affect the water vapor in the cylinder?

• Water molecules will move closer to each other, and the water vapor will change to liquid water.

• Water molecules will move farther away from each other, and the water vapor will change to liquid water.

• Water molecules will become smaller, and the water vapor will change to ice.

• Water molecules will become larger, and the water vapor will change to ice.

Answer explanation

As pressure increases while temperature remains constant, water molecules move closer together, leading to condensation. This causes the water vapor to change into liquid water.

Tags

NGSS.MS-PS1-4

Maria walked on a beach made mostly of sand. She walked barefoot on the beach early in the morning, and the sand was cool. When she walked in the same area in the afternoon, the sand was hot. Which statement best describes why the temperature of the sand increased?

• The atoms in the sand were moving more quickly.

• The sand had reflected the thermal energy of the water.

• The radiant energy of the sand had been lost to the air.

• The molecules in the sand formed tighter chemical bonds.

Answer explanation

The temperature of the sand increased because the atoms in the sand were moving more quickly as they absorbed heat from the sun, leading to a rise in temperature during the afternoon.

Tags

NGSS.MS-PS1-4

What has occurred when bubbles form in a liquid that is being heated?

• Oxygen has been absorbed from air.

• Heat has radiated through the liquid.

• Boiling point has been reached.

• Molecular stability has increased.

Answer explanation

Bubbles form in a heated liquid when the boiling point is reached, indicating that the liquid is transitioning to gas. This is a key sign of boiling, as the vapor pressure equals atmospheric pressure.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

NGSS.MS-PS3-5